This invention relates to the field of packaging liquid products and more particularly to a novel method and apparatus for conserving energy in the packaging of liquids such as carbonated beverages.
In the bottling or canning of carbonated beverages, it is necessary for the bulk liquid to be cooled prior to filling of the bottles or cans. Unless the bulk liquid is cooled to a temperature substantially below ambient, for example 35.degree.-40.degree. F., excessive foaming is encountered in the filling operation, causing spillage. Because of the necessity of cooling the bulk carbonated liquid to such relatively low temperatures, refrigeration is required. Typically, ammonia vapor compression refrigeration systems are used, although other refrigerants are suitable including, for example, Freon 12, Freon 22, and Freon 115. The bulk liquid may be cooled either by direct exchange with evaporating refrigerant or by means of an intermediate brine system.
After cans or bottles have been filled with cold liquid, it is essential to warm the containers to a temperature above the dew point of ambient air prior to packing of the containers in cartons if conventional cardboard type cartons are used. Otherwise, moisture formed by condensation on the outside surfaces of the containers infiltrates and causes deterioration of the cardboard cartons. The temperature to which the containers must be heated prior to packing in cartons, of course, varies with ambient conditions but as a rule of thumb cans or bare glass containers are typically heated to an internal liquid temperature of about 80.degree. F., while containers having an outer insulating plastic cover (such as Plastishield bottles) are heated to an internal liquid temperature of approximately 70.degree. F.
Heating of the containers is typically carried out in a so-called "warming machine". The containers are carried through the machine on a conveyor belt and either immersed in or sprayed with an aqueous warming solution. The solution is primarily water, containing a small percentage of an algicide. After heat is transferred from the solution to the containers, the solution is reheated and then recirculated to the container warming zone. Residual warming solution on the outside sufaces of containers exiting the machine is removed by a blast of warm air over the bottle surfaces.
The unfortunately conflicting requirements of first refrigerating the bulk liquid prior to the filling operation and thereafter warming the filled containers above the dew point results in substantial energy consumption, which represents a rapidly increasing cost in the bottling of carbonated beverages. A serious need, therefore, exists for techniques and equipment which may reduce the energy consumed in these operations.
Where the bulk carbonated liquid is cooled by means of vapor compression refrigeration utilizing a refrigerant such as ammonia, compressor discharge pressure is typically in the range of 180 to 190 psia so that the ammonia condensation temperature is typically on the order of 95.degree. F. Since this condensation temperature is normally above the ambient dew point and well above the temperature of the containers as filled, an energy savings can theoretically be accomplished by using the heat of condensation of the ammonia as a source of heat for warming the filled containers. It is understood that various attempts have been made in the art to implement such a scheme for energy recovery but, so far as is known, none has previously come to practical fruition. There is no practical technique for direct exchange of heat from condensing refrigerant to filled containers. It is theoretically feasible to recover this energy by heating the warming solution of a conventional container warming machine operation by employing it as a coolant in condensing the refrigerant. However, in view of the relatively narrow temperature differential between the condensing temperature of ammonia at 180-190 psia and the "ambient dew point," has heretofore rendered it has generally been considered impractical to use the heat of condensation of a refrigerant as an energy source for warming. In fact, warming machines typically operate with an inlet warming solution temperature in the range of 130.degree.-140.degree. F., which is not attainable through heating by ammonia condensation at the compressor discharge temperatures used in conventional ammonia refrigeration. Moreover, to maintain productivity, the flow of warming solution through the warming machine is normally maintained at a level such that the temperature drop of the solution is only 5.degree.-10.degree. F.